package com.xym.common.Converter;

import java.io.IOException;

import javax.servlet.http.HttpServletRequest;

import org.apache.commons.io.IOUtils;
import org.apache.commons.lang3.StringUtils;
import org.springframework.http.HttpOutputMessage;
import org.springframework.http.converter.HttpMessageNotWritableException;
import org.springframework.http.converter.json.MappingJackson2HttpMessageConverter;
import org.springframework.web.context.request.RequestContextHolder;
import org.springframework.web.context.request.ServletRequestAttributes;

import com.fasterxml.jackson.core.JsonEncoding;
import com.fasterxml.jackson.core.JsonProcessingException;

public class CallbackMappingJackson2HttpMessageConverter extends MappingJackson2HttpMessageConverter {

	// 做jsonp的支持的标识，在请求参数中加该参数
		private String callbackName;

		@Override
		protected void writeInternal(Object object, HttpOutputMessage outputMessage) throws IOException, HttpMessageNotWritableException {
			// 从threadLocal中获取当前的Request对象
			HttpServletRequest request = ((ServletRequestAttributes) RequestContextHolder.currentRequestAttributes()).getRequest();
			String callbackParam = request.getParameter(callbackName);
			if(StringUtils.isEmpty(callbackParam)){
				// 没有找到callback参数，直接返回json数据
				super.writeInternal(object, outputMessage);
			}else{
				JsonEncoding encoding = getJsonEncoding(outputMessage.getHeaders().getContentType());
				try {
					String result =callbackParam+"("+super.getObjectMapper().writeValueAsString(object)+");";
					IOUtils.write(result, outputMessage.getBody(),encoding.getJavaName());
				}
				catch (JsonProcessingException ex) {
					throw new HttpMessageNotWritableException("Could not write JSON: " + ex.getMessage(), ex);
				}
			}
			
		}

		public String getCallbackName() {
			return callbackName;
		}

		public void setCallbackName(String callbackName) {
			this.callbackName = callbackName;
		}
}
